linux-kernel - Re: [PATCH v4 00/10] hugetlbfs: add fallocate support

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Date:	Wed, 22 Jul 2015 16:18:30 -0700
From:	Mike Kravetz <mike.kravetz@...cle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Davidlohr Bueso <dave@...olabs.net>,
	Eric B Munson <emunson@...mai.com>
CC:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linux-api@...r.kernel.org,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	David Rientjes <rientjes@...gle.com>,
	Hugh Dickins <hughd@...gle.com>,
	Aneesh Kumar <aneesh.kumar@...ux.vnet.ibm.com>,
	Hillf Danton <hillf.zj@...baba-inc.com>,
	Christoph Hellwig <hch@...radead.org>,
	Michal Hocko <mhocko@...e.cz>
Subject: Re: [PATCH v4 00/10] hugetlbfs: add fallocate support

On 07/22/2015 03:30 PM, Andrew Morton wrote:
> On Wed, 22 Jul 2015 15:19:54 -0700 Davidlohr Bueso <dave@...olabs.net> wrote:
>
>>>
>>> I didn't know that libhugetlbfs has tests.  I wonder if that makes
>>> tools/testing/selftests/vm's hugetlbfstest harmful?
>>
>> Why harmful? Redundant, maybe(?).
>
> The presence of the in-kernel tests will cause people to add stuff to
> them when it would be better if they were to apply that effort to
> making libhugetlbfs better.  Or vice versa.
>
> Mike's work is an example.  Someone later makes a change to hugetlbfs, runs
> the kernel selftest and says "yay, everything works", unaware that they
> just broke fallocate support.
>
>> Does anyone even use selftests for
>> hugetlbfs regression testing? Lets see, we also have these:
>>
>> - hugepage-{mmap,shm}.c
>> - map_hugetlb.c
>>
>> There's probably a lot of room for improvement here.
>
> selftests is a pretty scrappy place.  It's partly a dumping ground for
> things so useful test code doesn't just get lost and bitrotted.  Partly
> a framework so people who add features can easily test them. Partly to
> provide tools to architecture maintainers when they wire up new
> syscalls and the like.
>
> Unless there's some good reason to retain the hugetlb part of
> selftests, I'm thinking we should just remove it to avoid
> distracting/misleading people.  Or possibly move the libhugetlbfs test
> code into the kernel tree and maintain it there.

Adding Eric as he is the libhugetlbfs maintainer.

I think removing the hugetlb selftests in the kernel and pointing
people to libhugetlbfs is the way to go.  From a very quick scan
of the selftests, I would guess libhugetlbfs covers everything
in those tests.

I'm willing to verify the testing provided by selftests is included
in libhugetlbfs, and remove selftests if that is the direction we
want to take.

-- 
Mike Kravetz
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